Abstract:

Recently, erbium-doped optical amplifiers have drawn significant attention as a solution to compensate the propagation losses for silicon photonics due to their ability to produce amplification of light at 1.5 um with high efficiency and low noise over wide bandwidth. In silicon photonics, much effort has been put into the development of Er-doped optical amplifiers in the form of strip or slot waveguides, in which the amplification is produced over short (~ cm) structures. However, there has not been any major success in the development, because several challenges arise in Er-doped waveguide amplifiers as the amplification over short structures requires very high concentration of Er-ions in the amplifier gain material. It has been shown that some of these challenges can be avoided by optimizing the fabrication of the Er-doped gain material. Atomic layer deposition has shown a great potential in the fabrication of Er-doped materials because it can be used to precisely control the profile of the Er-ions in the amplifier gain material.

In this thesis, plasma-enhanced atomic layer deposition has been successfully used to fabricate Er-doped materials and to control their photoluminescence 1.5 um This was done in two parts. First, an optimized ALD process for erbium in its sesquioxide form, Er2O3, was developed and as a result, a growth rate of 0.215 Å/cycle and non-uniformity of 3.55 % were obtained on 6" wafer. Er2O3 was then deposited in a nanolaminate configuration with Al2O3 and the thickness of the Al2O3 was controlled. The as-deposited samples were then optically characterized with absorption and photoluminescence measurements and it was observed that when the thickness of the Al2O3-layer between the Er2O3-layers was increased, an enhanced photoluminescence signal at 1.5 um was measured. Therefore, this thesis shows that the photoluminescence of the Er-ions at 1.5 um can be greatly enhanced by the nanoscale engineering of the fabrication process.Erbium-seostetut materiaalit ovat herättäneet kiinnostusta potentiaalisina materiaaleina valon vahvistamiseen ja valonlähteiksi piifotoniikassa. Piifotoniikassa valon teho vaimenee sekä sirujen välisissä kytkennöissä, että itse valokanavissa ja tämän takia signaalia täytyy vahvistaa. Myös halpojen, helposti integroitavien valonlähteiden puute on merkittävä ongelma piifotoniikassa. Jotta signaalin vavistus piipohjaisissa valokanavarakenteissa pystyttäisiin toteuttamaan, erbium-seostettuja materiaaleja on pyritty yhdistämään piifotoniikkaan. Valokanavissa törmätään kuitenkin erilaisiin haasteisiin, koska erbium-ionien määrää täytyy kasvattaa radikaalisti vahvistuksen aikaansaamiseksi lyhyillä matkoilla. Tästä syystä lisää tutkimusta ja uusia valmistustekniikoita tarvitaan erbium-pohjaisten valokanavavahvistimien toteuttamiseksi. Atomikerroskasvatusmenetelmä on erityisen potentiaalinen menetelmä erbium-pohjaisten materiaalien valmistamiseen, koska sillä voidaan tarkasti säätää erbium-ionien jakaumaa vahvistimen sisällä.